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TUFLOW NetCDF Raster Output Format: Difference between revisions

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=Introduction=
This page contains information on the NetCDF file format used for gridded (raster) outputs from a TUFLOW simulation. To specify NetCDF output from TUFLOW, the 2016 version or later of TUFLOW must be used and "NC" must be included in the Map Output Data Formats, e.g.<br>
<font color="blue"><tt>Map Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> xmdf nc </tt><font color="green"><tt>! Output both xmdf and NetCDF formats</tt></font><br>
<br>
Additional NetCDF related commands are:<br>
There are a range of additional NetCDF related commands, to control the output further these are:<br>
<font color="blue"><tt>NetCDF Output Compression </tt></font> <font color="red"><tt>==</tt></font><tt> {OFF} | ON | compression level <0 – 9>
<font color="blue"><tt>NetCDF Output Compression </tt></font> <font color="red"><tt>==</tt></font><tt> OFF | {ON} | compression level <0 – 9>
</tt><br>
<font color="blue"><tt>NetCDF Output Start Date </tt></font> <font color="red"><tt>==</tt></font><tt> {2000-01-01 00:00} | OFF | <date in isodate format>
Line 10 ⟶ 11:
</tt><br>
<font color="blue"><tt>NetCDF Output Direction </tt></font> <font color="red"><tt>==</tt></font><tt> {ANGLE} | BEARING</tt><br>
<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> {GenericFEWS} | FEWSGeneric</tt><br>
Br<br>
Please refer to the <u>[https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW manualManual]</u> for more details on these commands.
 
=File Format=
The output file has been created to work with GIS and the [http://www.delft-fews.nl/ Delft-FEWS software] and therefore should be compliant with the [http://cfconventions.org/ NetCDF CF 1.6 conventions]. It is noted that the [http://cfconventions.org/standard-names.html CF 1.6 standard names] do not include any allowance for number of the output names such as '''Hazard''' and '''Time of Peak''' but these are still output.<br>
There are two slightly different formats (<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> {Generic} | FEWS</tt>), which differ only in the storing of the [[TUFLOW_NetCDF_Raster_Output_Format#Non_Temporal_Variables | Non Temporal Variables]].
 
==Global Attributes==
ThereThe NetCDF file has four global attributes:<br>
* Title - The simulation name
* Source - The TUFLOW version which has been used
* References - The documentation of the NetCDF file, i.e. this page!
* Comment - A description of the output.
* NetCDF File Format Version - A unique value for file version, for the 2017 version this is 2.
* NetCDF Data Type - This is 1 for "NC" raster output and 2 for <u>[[TUFLOW_NetCDF_Cell_Centre_Output_Format | "NC" cell centered results]]</u>.
An example of the '''Global Attributes''' is:
<pre>
Line 30 ⟶ 35:
comment = 'Contains raster TUFLOW output, TUFLOW netcdf version: 1'
</pre>
 
==Dimensions==
The output NetCDF will have three or four dimensions depending on if the '''Generic''' or '''FEWS''' format has been specified. These are:
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* y - the number of y coordinates (rows of data)
* time - the number of outputs. Note that this is an unlimited dimension meaning that the number of time changes each time a new output is written
* static_time (FEWS Format only) - This has a valuesize of 1 and is used for storing thea time for the static_datastatic data (such as maximums)
An example of the '''Dimensions''' is:
<pre>
Line 45 ⟶ 51:
</pre>
==Variables==
All outputs for the simulation are written to a single NetCDF file. These are split into three categories:
Both time-varying and ??? variables are output in the same NetCDF file. For example if the model writes depths our every 10 minutes and tracking maximums is enabled (default) then two depth datasets are written: '''depths''' and '''maximum_depths'''.
* Common variables
===Standard Variables===
* Temporal variables
* Non Temporal variables.
For example if the model writes depths our every 10 minutes and tracking maximums is enabled (default) then two depth datasets are written: '''depths''' and '''maximum_depths'''. These are described further below.
 
===Common Variables===
For each simulation the following variables are written:<br>
* x - contains the x coordinates of the output grid
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* time - contains the times for the temporal outputs
* static time (FEWS only) - contains a single time which is used by FEWS to display the non time varying datasets (such as maximums)
Each of these variables has only a single dimension.
<pre>
time
Size: 7x1
Dimensions: time
Datatype: double
Attributes:
standard_name = 'time'
long_name = 'time'
units = 'hours since 2000-01-01 00:00'
axis = 'T'
y
Size: 467x1
Dimensions: y
Datatype: double
Attributes:
standard_name = 'projection_y_coordinate'
long_name = 'y-coordinate in cartesian system'
units = 'm'
axis = 'Y'
x
Size: 422x1
Dimensions: x
Datatype: double
Attributes:
standard_name = 'projection_y_coordinate'
long_name = 'x-coordinate in cartesian system'
units = 'm'
axis = 'X'
static_time
Size: 1x1
Dimensions: static_time
Datatype: double
Attributes:
standard_name = 'static_time'
long_name = 'static_time'
units = 'hours since 2000-01-01 00:00'
</pre>
 
===Temporal Result Variables===
For each of the map outputs data types specified in the control file, the outputs are written into a variable that has the dimensions x, y and time.<br>
For vector variables, this is split into two components, for example for the velocity output this is split into "magnitude_of_velocity" and "direction_of_velocity". The notation for the direction can be controlled with the command:<br>
<font color="blue"><tt>NetCDF Output Direction </tt></font> <font color="red"><tt>==</tt></font><tt> {ANGLE} | BEARING</tt><br>
<br>
An example of the temporal variables for a simulation with the h, d and v outputs is below:
<pre>
water_level
Size: 1946x856x161
Dimensions: x,y,time
Datatype: single
Attributes:
_FillValue = -999
depth
Size: 1946x856x161
Dimensions: x,y,time
Datatype: single
Attributes:
_FillValue = -999
magnitude_of_velocity
Size: 1946x856x161
Dimensions: x,y,time
Datatype: single
Attributes:
_FillValue = -999
direction_of_velocity
Size: 1946x856x161
Dimensions: x,y,time
Datatype: single
Attributes:
_FillValue = -999
</pre>
 
===StaticNon ResultTemporal Variables (single timestep)===
There are currently two output formats from TUFLOW, this is controlled with the command:<br>
<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> {GenericFEWS} | FEWSGeneric</tt><br>
The file formats are very similar, but for the FEWS format an(default) additionalthe timenon-temporal dimensionvariables and time variable "static_time" are used to storehave a time forassociated thewith maximumthem andto timeallow ofthem peakto datadisplay socorrectly that it loads into thein FEWS interface at an appropriate time.
For the generic output (which requires "<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> Generic</tt>"), the data is stored in an array that has the dimensions x and y:
 
<pre>
=Generic=
maximum_depth
This is the default output format and can also be specified by including "<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> Generic</tt>" in the .tcf file.
Size: 1946x856
 
Dimensions: x,y
=FEWS=
Datatype: single
To output in this format users will need to specify "<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> FEWS</tt>" in the .tcf file.
Attributes:
_FillValue = -999
</pre>
<br>
For the FEWS output (which is the default or has "<font color="blue"><tt>NetCDF Output Format </tt></font> <font color="red"><tt>==</tt></font><tt> FEWS</tt>" specified), the data is stored in an array that has the dimensions x, y and static_time:
<pre>
maximum_depth
Size: 1946x856x1
Dimensions: x,y,static_time
Datatype: single
Attributes:
_FillValue = -999
</pre>
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